The fundamental principles of magnetohydrodynamic (MHD) power generation are well known in the art. Reduced to essentials, an MHD generator operates by exposing a high-velocity stream of partially ionized gas to a transverse magnetic field, which separates the positive and negative ions; these positive and negative components are passed between electrodes, generating an electromotive force, which is then available for use.
A factor (parameter) which directly controls the power output of an MHD generator is the "ionization factor," which is defined as the ratio of ionized to neutral atoms within the gas stream. The dependence of the ionization factor (n.sub.i /n.sub.n) on the temperature of the gas is expressed by the Saha equation: ##EQU1## WHERE U.sub.i = ionization temperature of the gas
k = Boltzmann's constant PA1 T = temperature in kelvins
The foregoing expression indicates the desirability of developing as high a flame temperature as possible in order to maximize the higher ionization factor of a particular gas. As the electromotive force generated is a linear function of the number of ions collected on the electrodes per unit time, the power generated is essentially proportional to the number of ions produced, and hence, the flame temperature.
An alternative or additional method of improving the ionization factor n.sub.i /n.sub.n is to reduce U.sub.i -- that is, to use a material having lower ionization energy as the source of ions (i.e., a "seed") than that used as fuel. In such a case, the energy provided by the combustion of the fuel ionizes the seed material as, for example, is described in U.S. Pat. No. 3,873,860.
Typical prior art MHD power generation systems operate on an open cycle; that is, the fuel used is burned once, usually in air or oxygen. The exhaust product is then released to the atmosphere, and typically contains undesirable pollutants, such as SO.sub.2, CO, and the like. While attempts have been made to scrub the exhaust of such systems (e.g., U.S. Pat. No. 3,379,903), it would be preferable to provide a closed-cycle MHD power generation system which emits no pollutants as part of its plan of operation; in this way undesirable emissions could be reduced, theoretically, to zero.
A further difficulty with such prior art MHD power generation systems is that fossil fuels such as coal or oil are generally required. Presently known sources of these and other fossil fuels are not unlimited and it is therefore desirable to provide a power generation system which does not rely on the continued supply of such materials.